﻿using log4net;
using System;
namespace Velocity4Net.Runtime.Res
{

    /*
     * Licensed to the Apache Software Foundation (ASF) under one
     * or more contributor license agreements.  See the NOTICE file
     * distributed with this work for additional information
     * regarding copyright ownership.  The ASF licenses this file
     * to you under the Apache License, Version 2.0 (the
     * "License"); you may not use this file except in compliance
     * with the License.  You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing,
     * software distributed under the License is distributed on an
     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     * KIND, either express or implied.  See the License for the
     * specific language governing permissions and limitations
     * under the License.
     */













    /**
     * Default implementation of the resource cache for the default
     * ResourceManager.  The cache uses a <i>least recently used</i> (LRU)
     * algorithm, with a maximum size specified via the
     * <code>resource.manager.cache.size</code> property (identified by the
     * {@link
     * org.apache.velocity.runtime.RuntimeConstants#RESOURCE_MANAGER_DEFAULTCACHE_SIZE}
     * constant).  This property get be set to <code>0</code> or less for
     * a greedy, unbounded cache (the behavior from pre-v1.5).
     *
     * @author <a href="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
     * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
     * @version $Id: ResourceCacheImpl.java 1780734 2017-01-28 19:21:08Z cbrisson $
     */
    public class ResourceCacheImpl,ResourceCache
{

	/**
	 * A simple LRU Map based on {@link LinkedHashSet}.
	 *
	 * @param <K> The key type of the map.
	 * @param <V> The value type of the map.
	 */
	public  class LRUMap<K, V>:LinkedHashMap<K, V>{

		/**
		 * The size of the cache.
		 */
		private int cacheSize;

		/**
		 * Constructor.
		 *
		 * @param cacheSize The size of the cache. After reaching this size, the
		 * eldest-accessed element will be erased.
		 */
		public LRUMap(int cacheSize)
        {
	        this.cacheSize = cacheSize;
        }

		/** {@inheritDoc} */
		
        protected bool removeEldestEntry(Entry<K, V> eldest)
        {
	        return size() > cacheSize;
        }
	}

    /**
     * Cache storage, assumed to be thread-safe.
     */
    protected Map<Object, Resource> cache = new ConcurrentHashMap<>(512, 0.5f, 30);

    /**
     * Runtime services, generally initialized by the
     * <code>initialize()</code> method.
     */
    protected RuntimeServices rsvc = null;

    protected ILog log;

    /**
     * @see org.apache.velocity.runtime.resource.ResourceCache#initialize(org.apache.velocity.runtime.RuntimeServices)
     */
    public void initialize( RuntimeServices rs )
    {
        rsvc = rs;

        int maxSize =
            rsvc.getInt(RuntimeConstants.RESOURCE_MANAGER_DEFAULTCACHE_SIZE, 89);
        if (maxSize > 0)
        {
            // Create a whole new Map here to avoid hanging on to a
            // handle to the unsynch'd LRUMap for our lifetime.
            Map<Object, Resource> lruCache = Collections.synchronizedMap(new LRUMap<Object, Resource>(maxSize));
            lruCache.putAll(cache);
            cache = lruCache;
        }
        rsvc.getLog().Debug("initialized ({}) with {} cache map.", this.getClass(), cache.getClass());
    }

    /**
     * @see org.apache.velocity.runtime.resource.ResourceCache#get(java.lang.Object)
     */
    public Resource get( Object key )
    {
        return cache.get( key );
    }

    /**
     * @see org.apache.velocity.runtime.resource.ResourceCache#put(java.lang.Object, org.apache.velocity.runtime.resource.Resource)
     */
    public Resource put( Object key, Resource value )
    {
        return cache.put( key, value );
    }

    /**
     * @see org.apache.velocity.runtime.resource.ResourceCache#remove(java.lang.Object)
     */
    public Resource remove( Object key )
    {
        return cache.remove( key );
    }

    /**
     * @see org.apache.velocity.runtime.resource.ResourceCache#clear()
     * @since 2.0
     */
    public void clear()
    {
        cache.clear();
    }

    /**
     * @see org.apache.velocity.runtime.resource.ResourceCache#enumerateKeys()
     */
    public Iterator<Object> enumerateKeys()
    {
        return cache.keySet().iterator();
    }
}

}